2024 Volume 77 Issue 12 Pages e167-e172
A 12-year-old spayed female toy poodle presenting with a mild dry cough was admitted to our primary care veterinary hospital. Upon primary examination, her tongue exhibited a dark blue coloration which was indicative of cyanosis. Our initial diagnosis was a tracheal collapse. However, we were unable to ascertain the underlying etiology despite conducting a meticulous screening of her cardiopulmonary function. Subsequently, we hypothesized there were structural and functional abnormalities in her hemoglobin. Therefore, we performed genetic analyses looking at hemoglobin, nicotinamide adenine dinucleotide (NADH)-cytochrome b5 reductase (CYB5R3) and measured the methemoglobin in associated examinations. Consequently, a mutation was detected in the CYB5R3 gene. Additionally, an elevated methemoglobin concentration was observed, along with a decline in methemoglobin reductase activity and a reduction in reduced glutathione levels. The above observations confirmed the diagnosis of congenital methemoglobinemia.
